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I have this situation:

  • NTP is used to sync time on a set of Windows 7 and Server 2008 machines. Nothing out of the ordinary about this.
  • periodically on this system, the time needs to be changed for testing/training purposes (it is a training simulation system that has a lot of time-dependent operations).

My question:

As NTP in general does not really like big time jumps or changes AFAIK, is there a standard way this could be set up to allow the clock to be changed at the root NTP server in the system and have it propagate through the system in a reasonable amount of time (a minute or two?) It is not acceptable to disable and/or restart all NTP client services to achieve this.

Any ideas? It would be nice to do this without writing some kind of custom script to disable services and update clocks all over the place.

Thanks in advance.

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2 Answers 2

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How about isolating this group of time-travelling machines and pointing them to a dedicated NTPD service on a server with some spare resources?

There are NTP commands available to make/allow big NTP jumps, so you can either push them out over the network or embed them as local commands in your training simulation system/scripts?

Or disable NTP on these machines altogether and obtain complete set time/date freedom?

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  • Thanks for your comment - So these machines will have their own NTP server - I guess what I want to know is can an NTP client/server be set up to automatically handle these jumps, without having to run a specific set of commands, or build other scripts etc? I'd like the users to be able to set one clock to their desired time and have it all just work.
    – Gerard
    Jan 6, 2011 at 21:35
  • Its preferable also to not remove NTP from the system in the "normal" non-time-travelling case.
    – Gerard
    Jan 6, 2011 at 21:37
  • You could allow the endusers to change the system time (through group policies), and schedule a local task to set the clock to the correct time outside office hours. I'm not sure you can achieve for one enduser to change all clocks at once without scripting. Powershell and it's remote powers would be neat for this.
    – DutchUncle
    Jan 6, 2011 at 21:51
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Best I can suggest is to find HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient on the clients and change SpecialPollInterval to some small poll interval (decimal, units are seconds).

As for the big jumps part, UNIX/Linux has the ntpdate command to allow for a big jump, usually executed just before the ntpd starts running to keep the skew in check. The only thing I can find for Windows 7 that is remotely similar is w32tm.exe /resync (part of the OS).

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